Field of the Invention
The present invention relates to a technique for measuring the three-dimensional shape of an object.
Description of the Related Art
A technique of measuring the three-dimensional shape of an object or the distortion of a surface by projecting a predetermined pattern onto the object and calculating the distortion of the predetermined pattern from a captured image is conventionally implemented. Particularly, there is well known a method capable of measuring the three-dimensional shape of an object or the degree of distortion of a surface by projecting a random pattern onto the object and calculating a local displacement amount by correlation calculation. Under the condition that the position of the object falls outside the imaging range of the pattern, however, a blur occurs in the projected pattern to decrease the contrast, thereby disabling accurate measurement.
To solve this problem, there is proposed an adaptive method of evaluating an image of an object onto which a pattern has been projected, and switching, when it is determined that the pattern is inappropriate, the pattern to another pattern. Japanese Patent Laid-Open No. 2001-147110 describes a method of projecting a pattern onto an object having a texture, evaluating whether the pattern is appropriate, and switching, if the pattern is inappropriate, the pattern to another pattern. This method is applicable to not only the texture of the object but also a blur.
The above conventional technique, however, requires a projection apparatus capable of arbitrarily changing a pattern to be projected, and it is thus necessary to use an expensive image projector with a complicated structure or the like. Furthermore, it takes time to switch a pattern, and the number of images to be shot increases.